<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
</head>

<body>
    <p>
        <input type="text" name="a" />
    </p>
    <p>
        <input type="file" name="img" accept="image/*" multiple />
    </p>
    <p>
        <button>提交</button>
    </p>
    <img src="" alt="" />
    <script>
        function upload(e) {
            // e.preventDefault()
            const inpA = document.querySelector("[name=a]");
            const inpFile = document.querySelector("[name=img]");
            const img = document.querySelector("img");
            const formData = new FormData(); //帮助你构建form-data格式的消息体
            formData.append("a", inpA.value);
            for (const file of inpFile.files) {
                formData.append("file", file, file.name);
            }
            fetch("/upLoad", {
                body: formData,
                method: "POST",
            })
                .then((resp) => resp.json())
                .then((resp) => {
                    console.log(resp);
                    if (resp.code) {
                        //有错误
                        alert(resp.msg);
                    } else {
                        img.src = resp.data.url;
                    }
                });
        }

        document.querySelector("button").onclick = upload;
    </script>
</body>

</html>